482 THE SENSORIAL FUNCTIONS. 



only by an isolated portion of the spinal cord, at a 

 great distance from the brain, and by it transmitted 

 to the motor nerves. Similar phenomena may be 

 produced by galvanism in detached portions of the 

 human body. Hence it appears that motions may 

 occur, which imitate the natural voluntary move- 

 ments, and yet are wholly of a mechanical or auto- 

 matic nature : the occurrence of such notions, 

 therefore, is no proof of sensibility or percipience. 



The sensorial functions, nevertheless, seem to 

 require some common nervous centre, or sensorium, 

 where the actions connected with sensation, per- 

 ception and volition are carried on : for it is hardly 

 possible to conceive that the sensorium can be 

 divided into separate portions acting independently 

 of one another ; such separation being incom- 

 patible with every idea that can be formed of 

 individuality of being. We may, however, under- 

 stand how the different portions of the nervous 

 system, although separated by wide intervals, may, 

 by means of the commissural fibres, be brought 

 into immediate connexion with one another, and 

 rendered capable of co-operation in one consen- 

 taneous mode of action. 



The analysis I have now given of these complex 

 functions, will assist us in understanding the eco- 

 nomy of the nervous system in the different forms 

 under which it exists in the several classes of 

 animals. 



